General Construction; Principle Of Operation; Hydrokinetic Drive; Chemical And Atex Compliant Eh Pumps - Edwards EH500 Instruction Manual

A301-51-880 Issue T
Figure 1 - All EH250 and EH500 pump variants
1. Terminal-box
2. Shaft-seal reservoir vented oil filler-plug
3. Hydrokinetic drive/gearbox oil filler-plug
4. Inlet-flange
5. External evacuation point
6. End-cover
7. Rotors
8. Stator housing
9. Hydrokinetic drive/gearbox oil drain-plug (under the pump)
10. Direction of rotation sight-glass
11. Oil-level sight-glass (hydrokinetic drive/gearbox)
12. Oil-level sight-glass (shaft-seal reservoir)
© Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
A301-51-880 Issue T
1.2.2

General construction

The EH pumps are positive displacement Roots vacuum pumps. The pump mechanism is driven by a three-phase
electric motor through a hydrokinetic drive (see Section 1.2.4).
The safe area EH pumps are all fitted with safe area motors. The chemical, and ATEX compliant EH pumps are all
fitted with flameproof motors (see Section 1.3.1). All of the motors are air-cooled.
The pump shafts and rotors are made of cast SG iron. The internal and external shaft-seals are made of
polytetrafluoroethylene (PTFE) or fluoro-elastomer.
The pump-bearings, gears and seals are lubricated by oil fed from reservoirs in the hydrokinetic drive/gearbox. A
series of seals stops the oil from reaching the vacuum side of the EH pump. The hydrokinetic drive/gearbox is
evacuated. You can inspect the oil-levels through sight-glasses which are fitted to the hydrokinetic drive/gearbox.
Oil-filler, oil-drainage and external evacuation connections are provided on the hydrokinetic drive/gearbox.
The timing gears on all of the EH1200, EH2600 and EH4200 model pumps are lubricated by oil inside the gear-cover.
An oil-filler connection is provided and you can inspect the oil-level through a sight-glass fitted to the gear-cover.
1.2.3

Principle of operation

The EH pump is shown in Figure 1 and 2. The motor-shaft drives one of the rotors through the hydrokinetic drive. The
1:1 gears inside the hydrokinetic drive/gearbox drive the second rotor in the opposite direction inside the stator
housing. A small, accurately gauged, clearance is maintained between the rotors and between each rotor and the
stator wall. This clearance allows the EH pump to operate at high speed without mechanical wear and without the
need for lubrication inside the swept volume.
1.2.4

Hydrokinetic drive

The hydrokinetic drive consists of a fluid-coupling which connects the electric-motor shaft to the rotor. This system
is configured so that when the gas-load is high, the rotational speed of the rotors is reduced. As the gas-load
decreases, the rotors accelerate to full speed. This allows continuous operation of the EH pump over the vacuum
range without the risk of overloading the motor and removes the need for bypass-valves and associated pipelines.
The fluid-coupling is viscosity sensitive. The two versions of the EH pump (for hydrocarbon and PFPE oils) have fluid-
coupling drives which are specifically designed for the type of oil used in the pump.
1.3

Chemical and ATEX compliant EH pumps

1.3.1

Flameproof motors

All of the EH1200C, EH1200 T3/T160/T4X, EH2600C, EH2600T3X, EH2600 T160/T4X, EH4200C, EH4200 T3X and
EH4200 T160/T4X:
Pumps suitable for 50 Hz operation are fitted with a flameproof motor approved to EEx d, Gas Group IIA, IIB,
Temperature Class T4.
Pumps suitable for 60 Hz operation are fitted with a flameproof motor approved to CSA, Division 1 area, Gas
Class I Group C & D, and Dust Class II Group F & G, Temperature Class T3C.
If you want to operate your pump in a IIC external environment you have to fit a IIC motor to your EH
mechanical booster.
© Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Page 3
Page 5
A301-51-880 Issue T
Figure 2 - All EH1200, EH2600 and EH4200 pump variants
A. All EH2600 and EH4200 pumps
B. All EH1200 pumps
1. Terminal-box
2. Shaft-seal reservoir vented oil filler-plug
12. Stator housing
3. Cooling-water connection
13. Hydrokinetic drive/gearbox oil drain-plug
4. Hydrokinetic drive/gearbox oil filler-plug * (under the pump)
5. Inlet-flange †
14. Direction of rotation sight-glass
6. External evacuation point
15. Oil-level sight-glass (hydrokinetic drive/
7. Gear-cover oil filler-plug gearbox)
8. Cooling-water connection
16. Oil-level sight-glass (shaft-seal reservoir)
9. Oil-level sight-glass (gear-cover)
17. Motor fan cover
10. Gear-cover oil drain-plug (under the pump)
11. Rotors
† EH1200 pumps only.
* Safe area EH pumps only. On the chemical,
and ATEX compliant EH pumps, this is a
combined hydrokinetic drive/gearbox oil
filler-plug and purge connector.
Page 4 © Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
A301-51-880 Issue T
1.3.2

ATEX directive (94/9/EC): Europe only

ATEX compliant EH pumps with an internal T3X or T160/T4X temperature classification (see Section 1.3.3) may be
used in an ATEX-compliant vacuum system only if the pumps are configured and used in accordance with the
requirements of this manual. For ATEX compliant systems using an EH booster pump in combination with a DPS dry
pump also the requirements of the ATEX instruction manual (see 'Associated publications' at the end of the Contents
list) must be met.
Note: An 'X' suffix to the EH booster ATEX classification indicates that there are special conditions for safe use of
the booster. For EH mechanical boosters that have not been sold as part of a Edwards approved ATEX system
please give special attention to Section 2.2 and Table 2 and 3.
ATEX compliant systems supplied by Edwards will be certified in accordance with the ATEX directive, and will be
identified by an ATEX system rating label.
If you want to fit an ATEX compliant EH pump with a T3X or T160/T4X temperature classification into your own ATEX
compliant vacuum system, you must install and operate the EH pump in accordance with the requirements of this
instruction manual. Please pay special attention to Section 1.3.3 about the temperature classification of your EH
pump, Section 1.3.4 about the hydrokinetic gearbox purge, Section 1.3.6 about the requirements of constructional
safety, Section 1.3.7 abnormal use, Section 2.2 about the critical backing pressure and the pressure ratio between
your EH mechanical booster pump and your backing pump and Section 2.8 about the minimum cooling water flow.
You must also carry out your own Safety Risk Assessment as part of your system certification in order to ensure that
your system is safe. If necessary, contact Edwards for certification advice.
ATEX compliant EH pumps with an internal T3X or T160/T4X temperature classification are suitable for operation in
ATEX compliant systems rated as follows:
II 2 G c IIB T3 II 2 G c IIB T160/T4
or
The notations used in these ratings are as follows:
specifies that the ATEX compliant EH pump can be used in a potentially explosive
atmosphere.
II Equipment group II
2G
Equipment category 2 (gas)
c constructional safety
IIB Suitable to pump gas group IIB
T3/T160/T4 Gas auto-ignition temperature: see Section 1.3.3.
Refer to Section 2 of this manual for the necessary EH pump operating conditions, and, if your booster is part of a
Edwards vacuum system, to the ATEX Instruction manual and to your system instruction manual for specific details
of the system.
Note: If the system rating has an "X" suffix, this indicates that there are special conditions for the safe use of your
system: refer to the ATEX Instruction Manual and to your system manual for details.
1.3.3

Temperature classification

The temperature classifications applied to the chemical and ATEX compliant EH pumps relate to the auto-ignition
temperature of flammable materials that can be pumped:
The EH1200, EH2600, EH4200, ATEX compliant and chemical EH pumps that have a T3 classification are
suitable for pumping flammable materials that have an auto-ignition temperature greater than 200
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